The long term goal of this project is to map the olfactory bulb (OB) input patterns of brain regions that receive direct mitral and tufted (M/T) cell input from the OB using transsynaptic tracing. In order to understand the neural basis of olfactory perception, it is necessary to elucidate the relationship of the OB to the olfactory cortex (OC). Little is known about the critical question of how distributed OB input is organized in the OC. Recently developed synaptic tracing tools, advances in the sensitivity obtainable from classical tracers, greater computational reconstruction capabilities, and availability of functional data all suggest that revisiting the previous neuroanatomical studies is worthwhile. Using new retrograde transsynaptic tracing techniques, we demonstrated in previous work that the modular organization of the OB glomerular connectivity unit extends in a well defined column structure from the glomerulus to the deep granule cell layer. We found each of the minimal columns to be associated with a single glomerulus, while the larger columns are thought to arise from multiple glomeruli. These columns were found after injection of either the OB or the anterior piriform cortex and resulted in specific patterns of labeled glomerular modules. I propose to use the labeled column as an indicator of glomerular unit output through mitral and tufted cells to injected regions of olfactory cortex. The overall aim of this application is to test the hypothesis that inputs from the olfactory bulb are topographically organized in the olfactory cortex. This will provide the first quantitative evidence of the extent to which there is inter-regional OB input segregation, the degree of OB input as a function of distance, and whether OB input patterns are spatially conserved across individuals in the OC regions selected for this application. Information processing through the OC plays an important role in many human diseases, including obesity, and anosmias. It is one of the first brain regions to show indications of Alzheimer's and Parkinson's, and is particularly susceptible to epileptogenesis. A more thorough knowledge of OC connectivity relationships will form a foundation to better understand olfactory information processing and OC contributions to these diseases. This project proposes to map neural connections of the olfactory cortex (OC) to better understand information processing by the cortex. Information processing through the OC plays an important role in many human diseases, including obesity, and anosmias (inability to smell). It is one of the first brain regions to show indications of Alzheimer's and Parkinson's, and is particularly susceptible to epilepsy. A more thorough knowledge of OC connectivity relationships will form a foundation to better understand olfactory information processing and OC contributions to these diseases.